Taittirīyopaniṣat 01.11

आ मा यन्तु ब्रह्मचारिणः स्वाहा। वि मा यन्तु ब्रह्मचारिणः स्वाहा। प्र मा यन्तु ब्रह्मचारिणः स्वाहा। द मा यन्तु ब्रह्मचारिणः स्वाहा। श मा यन्तु ब्रह्मचारिणः स्वाहा। यशोजनेनानि स्वाहा। श्रेयान् वस्यसोऽसानि स्वाहा। तं त्वा भग प्रविशानि स्वाहा। स मा भग प्रविश स्वाहा। तस्मिंत्सहस्रशाखे। नि भगाहं त्वयि मृजे स्वाहा ॥११॥

"Invoking the syllable 'Aa', i.e. auspicious expansion, may the brahmachārins (students) come to me, Offering!
Invoking the syllable 'Vi', i.e. distinguished particularity, may the brahmachārins (students) come to me, Offering!
Invoking the syllable 'Pra', i.e. with directedness and intensity, may the brahmachārins (students) come to me, Offering!
Invoking the syllable 'Da', i.e. self-control, may the brahmachārins (students) come to me, Offering!
Invoking the syllable 'Sha', i.e. tranquillity, may the brahmachārins (students) come to me, Offering!
Glory to all the people, Offering!
Let there be enhanced prosperity, Offering!
O Lord, may I enter you, Offering!
O Lord, may you enter me, Offering!
In that thousand-branched (body); O Lord, I cleanse myself in you, Offering!